#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
char s[maxn];
char p[4]={"RGB"};
int main(void){
   	cin.tie(0);std::ios::sync_with_stdio(false);
    LL n;cin>>n;
    for(LL i=1;i<=n;i++) cin>>s[i];
    LL ans=0;
    for(LL i=2;i<=n;i++){
        if(s[i]==s[i-1]){
            char tmp=s[i+1];
            for(int j=0;j<3;j++){
                if(s[i-1]!=p[j]&&p[j]!=tmp){
                    s[i]=p[j];
                    ans++;
                    break;
                }
            }
        }
    }
    cout<<ans<<endl;
    for(LL i=1;i<=n;i++){
        cout<<s[i];
    }cout<<endl;
   	return 0;
}
